All questions of Percentages for Mechanical Engineering Exam

Weight of A and B are in the ratio of 3:5. If the weight of A is increased by 20 percent and then the total weight becomes 132 kg with an increase of 10 percent. B weight is increased by what percent.
  • a)
    2%
  • b)
    3%
  • c)
    4%
  • d)
    5%
  • e)
    None of these
Correct answer is option 'C'. Can you explain this answer?

Answer – 3. 4% Explanation : Weight of A and B are 3x and 5x.
Initial weight before increase = (132*100)/110 = 120 8x = 120. X = 15 Initial weight of A and B are 45 and 75 kg respectively.
New weight of A = 54 so weight of B = 132 – 54 = 78.
So % increase = [(78-75)/75]*100 = 4 %

 A vendor sells 50 percent of apples he had and throws away 20 percent of the remainder. Next day he sells 60 percent of the remainder and throws away the rest. What percent of his apples does the vendor throw?
  • a)
    20%
  • b)
    22%
  • c)
    24%
  • d)
    26%
  • e)
    None of these
Correct answer is option 'D'. Can you explain this answer?

Let the total number of apples the vendor initially had be 100 (for simplicity).
On the first day:
The vendor sells 50% of the apples:
Apples sold on day 1 = 50% of 100 = 50
The remaining apples after selling 50% are:
Remaining apples = 100 − 50 = 50
He then throws away 20% of the remaining apples:
Apples thrown away on day 1 = 20% of 50 = 10
The remaining apples after throwing away 20% are:
Remaining apples after day 1 = 50 − 10 = 40
On the second day:
The vendor sells 60% of the remaining apples:
Apples sold on day 2 = 60% of 40 = 24
The remaining apples after selling 60% are:
Remaining apples after selling on day 2 = 40 − 24 = 16
He throws away the rest, which is 16 apples.
Total apples thrown away:
Apples thrown away on day 1 = 10
Apples thrown away on day 2 = 16
Total apples thrown away = 10 + 16 = 26
Percentage of apples thrown away:

Thus, the vendor throws away 26% of his apples.

In a library, 30% of the books are in History. 50% of the remaining are in English and 40% of the remaining are in German. The remaining 4200 books are in regional languages. What is the total number of books in library?
  • a)
    10000
  • b)
    15000
  • c)
    20000
  • d)
    25000
  • e)
    None of these
Correct answer is option 'C'. Can you explain this answer?

Let the total number of books in the library be T.
30% of the books are in History:
History books = 30% of T = 0.30 × T
The remaining books after accounting for History are:
Remaining books = T − 0.30 × T = 0.70 × T
50% of the remaining books are in English:
English books = 50% of the remaining = 0.50 × 0.70 × T = 0.35 × T
After accounting for English books, the remaining books are:
Remaining books after English = 0.70T − 0.35T = 0.35T
40% of the remaining books are in German:
German books = 40% of the remaining = 0.40 × 0.35 × T = 0.14 × T
After accounting for German books, the remaining books are:
Remaining books after German = 0.35T − 0.14T = 0.21T
The remaining 4200 books are in regional languages, so:
0.21 × T = 4200
Solving for T:
T = 4200/0.21 = 20000
Thus, the total number of books in the library is 20,000.

When the price of rice is increased by 25 percent, a family reduces its consumption such that the expenditure is only 10 percent more than before. If 40 kg of rice is consumed by family before, then find the new consumption of family.
  • a)
    34.2
  • b)
    35.2
  • c)
    36.2
  • d)
    37.2
  • e)
    None of these
Correct answer is option 'B'. Can you explain this answer?

Rhea Reddy answered
Answer – 2.35.2 Explanation : Suppose initially price per kg of rice is 100 then their expenditure is 4000.
Now their expenditure is only increased by only 10% i.e – 4400.
Increased price of rice = 125.
So new consumption = 4400/125 = 35.2

40% of the women are above 30 years of age and 80 percent of the women are less than or equal to 50 years of age. 20 percent of all women play basketball.If 30 percent of the women above the age of 50 plays basketball, what percent of players are less than or equal to 50 years?
  • a)
    50%
  • b)
    60%
  • c)
    70%
  • d)
    80%
  • e)
    None of these
Correct answer is option 'C'. Can you explain this answer?

Let the total number of women be 100 (for simplicity).
Women above 30 years of age:
40% of the women are above 30 years of age, which means:
Women above 30 years = 40% of 100 = 40 women
Women less than or equal to 50 years of age:
80% of the women are less than or equal to 50 years of age, which means:
Women less than or equal to 50 years = 80% of 100 = 80 women
Women above 50 years of age:
Since 80% are less than or equal to 50 years, the remaining 20% are above 50 years of age, which means:
Women above 50 years = 20% of 100 = 20 women
Women who play basketball:
20% of all women play basketball, which means:
Total basketball players = 20% of 100 = 20 women
Women above 50 years of age who play basketball:
30% of the women above 50 years play basketball, which means:
Basketball players above 50 years = 30% of 20 = 6 women
Women less than or equal to 50 years who play basketball:
The total number of basketball players is 20, and 6 of them are above 50 years of age.
Therefore, the number of players less than or equal to 50 years of age is:
Basketball players less than or equal to 50 years = 20 − 6 = 14 women
Percentage of players who are less than or equal to 50 years of age:
Percentage of players less than or equal to 50 years = 
Thus, 70% of the basketball players are less than or equal to 50 years of age.

 60 percent of the employees of a company are women and 75% of the women earn 20000 or more in a month. Total number of employees who earns more than 20000 per month in the company is 60 percent of the total employees.What fraction of men earns less than 20000 per month?
  • a)
    5/8
  • b)
    5/7
  • c)
    1/5
  • d)
    3/4
  • e)
    None of these
Correct answer is option 'A'. Can you explain this answer?

Total employees = 100 (for simplicity).
Number of women = 60% of 100 = 60 women.
Number of men = 40% of 100 = 40 men.
75% of the women earn 20,000 or more:
Women earning 20,000 or more = 75% of 60 = 0.75 × 60 = 45 women.
Total number of employees earning more than 20,000 per month is 60% of the total employees:
Employees earning more than 20,000 = 60% of 100 = 60 employees.
Out of these 60 employees, 45 are women, so the remaining 15 must be men:
Men earning more than 20,000 = 15 men.
The total number of men is 40, and 15 men earn more than 20,000, so the number of men earning less than 20,000 is:
Men earning less than 20,000 = 40 − 15 = 25 men.
The fraction of men earning less than 20,000 is:
Fraction = 25/40 = 5 / 8
Thus, the correct answer is A: 5/8

 In an election contested by two parties A and B, party A secured 25 percent of the total votes more than Party B. If party B gets 15000 votes. By how much votes does party B loses the election?
  • a)
    8000
  • b)
    10000
  • c)
    12000
  • d)
    15000
  • e)
    None of these
Correct answer is option 'B'. Can you explain this answer?

Answer – b) 10000 Explanation : Let total votes = T and party B gets 15000 votes then party A will get T -15000 votes T – 15000 – 15000 = 25T/100
T = 40000, so A get 25000 and B gets 15000 votes, so difference = 10000

Alisha goes to a supermarket and bought things worth rupees 60, out of which 40 paise went on sales tax. If the tax rate is 10 percent, then what was the cost of tax free items?
  • a)
    54.60
  • b)
    55.60
  • c)
    56.60
  • d)
    57.60
  • e)
    None of these
Correct answer is option 'B'. Can you explain this answer?

Total cost of items = ₹60.
Sales tax paid = 40 paise = ₹0.40.
Tax rate = 10%. So, the tax amount is 10% of the cost of taxed items (denoted as T).
The sales tax equation is:

Solving for T:
Now, the cost of tax-free items is:
Cost of tax-free items = 60 − T − Sales tax = 60 − 4 − 0.40 = 55.60 rupees.
Thus, the cost of tax-free items is ₹55.60.

In a library 5 percent books are in English, 10 percent of the remaining are in hindi and 15 percent of the remaining are in Sanskrit. The remaining 11628 books are in French. Then find the total number of books in the library.
  • a)
    8000
  • b)
    12000
  • c)
    16000
  • d)
    20000
  • e)
    None of these
Correct answer is option 'C'. Can you explain this answer?

Ravi Singh answered
5% of books are in English,
10% of remaining books are in Hindi,
15% of remaining books are  in Sanskrit. 
Remaining books are in french = 11628
Calculation:
Let the total books in the library be 100%
According to question:
5% of books are in English
Remaining books = 100 - 5 = 95%
10% of remaining are in hindi = 10% of 95 = 9.5
Remaining books = 95 - 9.5 = 85.5%
15% of remaining books are in sanskrit = 15% of 85.5 = 12.825%
Remaining books = 85% - 12.825% = 72.675%
According to question:
72.675% = 11628
⇒ 1% = (11628/72.675)
⇒ 100% = (11628/72.675)× 100 = 16000
∴ Required value = 16000

When the price of rice is increased by 30 percent, a family reduces its consumption such that the expenditure is only 20 percent more than before. If 50 kg of rice is consumed by family before, then find the new consumption of family (approx.)
  • a)
    43kg
  • b)
    44kg
  • c)
    45kg
  • d)
    46kg
  • e)
    None of these
Correct answer is option 'D'. Can you explain this answer?

Answer – 4.46kg Explanation : Suppose initially price per kg of rice is 100 then their expenditure is 5000.
Now their expenditure is only increased by only 20% i.e – 6000.
Increased price of rice = 130.
So new consumption = 6000/130 = 46.1

The population of a village has increased annually at the rate of 20%. If at the end of 3 years it is 21600, the population in the beginning of the first year?
  • a)
    10000
  • b)
    12500
  • c)
    15000
  • d)
    17500
  • e)
    None of these
Correct answer is option 'B'. Can you explain this answer?

Divey Sethi answered
We can use the formula for compound growth to find the initial population:
where:
  • P is the final population (21600)
  • P0 is the initial population (what we want to find)
  • r is the annual growth rate (20% or 0.20)
  • n is the number of years (3)
Plug in the known values:

Simplify and solve for P0:

The population of a village has increased annually at the rate of 20%. If at the end of 3 years it is 21600, the population in the beginning of the first year?
  • a)
    10000
  • b)
    12500
  • c)
    15000
  • d)
    17500
Correct answer is option 'B'. Can you explain this answer?

  • The population increases by 20% annually, meaning it multiplies by 1.20 each year.
  • After 3 years, the population is 21600.
  • Using the compound growth formula P=P0(1+r)t, where P = 21600, r = 0.20, and t = 3, we calculate the initial population P0.
  • Solving 21600=Px (1.20)3, we find P= 12500.
  • The initial population is therefore 12500.

30 litre of solution contains alcohol and water in the ratio 2:3. How much alcohol must be added to the solution to make a solution containing 60% of alcohol?
  • a)
    10
  • b)
    12
  • c)
    14
  • d)
    15
  • e)
    None of these
Correct answer is option 'D'. Can you explain this answer?

The initial solution contains 30 liters, with alcohol and water in the ratio 2:3.
The amount of alcohol in the solution is:

The amount of water in the solution is:
We need to add some amount of alcohol (let it be x) to make the alcohol content 60% of the total solution.
After adding x liters of alcohol, the new total volume of the solution will be 30 + x liters, and the amount of alcohol will be 12 + x liters.
The concentration of alcohol should be 60%, so:

Solving the equation:
Thus, 15 liters of alcohol must be added to the solution.

 A man spends 60% of his income. His income is increased by 20% and his expenditure also increases by 10%. Find the percentage decrease in his saving?
  • a)
    10%
  • b)
    15%
  • c)
    20%
  • d)
    25%
  • e)
    None of these
Correct answer is option 'A'. Can you explain this answer?

Rhea Reddy answered
Answer – a) 10% Explanation : Let initially income is 100. So, expenditure = 60 and saving = 40 now income is increased by 20% i.e. 120. So, expenditure = (70/100)*120 = 84 and saving = 36 so % percent decrease in saving = (4/40)*100 = 10%

The number of seats in a cinema hall is decreased by 8% and also the price of the ticket is increased by 4 percent. What is the effect on the revenue collected?
  • a)
    increase 4.32%
  • b)
    decrease 4.32%
  • c)
    increase 3.32 percent
  • d)
    decrease 3.32%
  • e)
    None of these
Correct answer is option 'B'. Can you explain this answer?

Answer – b) decrease 4.32% Explanation : Let initially seats are 100 and price of each seat is 100, so total initial revenue = 10000
now, seats are 92 and price of each seat = 104, so total revenue = 92*104 = 9568 so percent change in revenue = (432/10000)*100 = 4.32 decrease

 Weights of two friends A and B are in the ratio of 1 : 2. A’s weight increases by 20% and the total weight of A and B together becomes 60 kg, with an increase of 30%. By what percent the weight of B increase?
  • a)
    30%
  • b)
    35%
  • c)
    40%
  • d)
    45%
  • e)
    None of these
Correct answer is option 'B'. Can you explain this answer?

Let the original weights of A and B be A and B, respectively. Since the ratio of their weights is 1 : 2, we can say:
A = x and B = 2x
A’s weight increases by 20%, so the new weight of A is:
New weight of A = A + 20% of A = x + 0.20x = 1.2x
The total weight of A and B after the increase is 60 kg, and it is also given that the total weight increased by 30%. Therefore, the original total weight of A and B was:
Original total weight = 60/1.30 = 46.15 kg (approximately)
The original total weight of A and B is also A + B = x + 2x = 3x, so:
3 x = 46.15 ⇒ x = 46.15/3 = 15.38 kg (approximately)
So, A’s original weight is approximately 15.38 kg, and B’s original weight is:
B = 2x = 2 × 15.38 = 30.76 kg (approximately)
The new total weight is 60 kg, and the new weight of A is 1.2x = 1.2 × 15.38 = 18.46 kg. Therefore, the new weight of B is:
New weight of B = 60 − 18.46 = 41.54 kg (approximately)
Now, we can calculate the percentage increase in B’s weight:
Thus, B’s weight increased by 35%.

In an examination 70% candidates passed in prelims and 55% candidates passed in Mains. If 62% candidates passed in both these subjects, then what per cent of candidates failed in both the exams?
  • a)
    37%
  • b)
    26%
  • c)
    43%
  • d)
    15%
  • e)
    None of these
Correct answer is option 'A'. Can you explain this answer?

Rajeev Kumar answered
Answer – 1.37% Explanation : Students passed in Prelims = 70% Students passed in Mains = 55% Students passed in both  = 62% No of students passed in at least one subject = (70+55)-62 = 63%. students failed in both subjects = 100-63 = 37%.

The number of seats in a cinema hall is decreased by 8% and also the price of the ticket is increased by 4 percent. What is the effect on the revenue collected?
  • a)
    increase 4.32%
  • b)
    decrease 4.32%
  • c)
    increase 3.32 percent
  • d)
    decrease 3.32%
Correct answer is option 'B'. Can you explain this answer?

EduRev GATE answered
Let initially seats are 100 and price of each seat is 100, so total initial revenue = 10000
now, seats are 92 and price of each seat = 104, so total revenue = 92*104 = 9568
so percent change in revenue = (432/10000)*100 = 4.32 decrease

Alisha goes to a supermarket and bought things worth rupees 60, out of which 40 paise went on sales tax. If the tax rate is 10 percent, then what was the cost of tax free items?
  • a)
    54.60
  • b)
    55.60
  • c)
    56.60
  • d)
    57.60
Correct answer is option 'B'. Can you explain this answer?

Niharika Basu answered
Calculation of Tax-Free Items Cost:
Explanation:
- Total cost of items = Rs. 60
- Sales tax = 40 paise
- Tax rate = 10%

Step 1: Calculate the total tax amount
- Tax rate = 10%
- Total cost of items = Rs. 60
- Tax amount = 10% of Rs. 60 = Rs. 6

Step 2: Convert the tax amount to paise
- 1 Rupee = 100 paise
- Rs. 6 = 6 * 100 = 600 paise

Step 3: Calculate the tax-free items cost
- Total cost of items = Rs. 60 = 6000 paise
- Sales tax = 40 paise
- Total tax amount = 600 paise
- Cost of tax-free items = Total cost of items - Total tax amount
- Cost of tax-free items = 6000 paise - 600 paise = 5400 paise = Rs. 54
Therefore, the cost of the tax-free items is Rs. 54.60, which is option 'B'.

The prices of two articles are in the ratio 3 : 4. If the price of the first article be increased by 10% and that of the second by Rs. 4, the original ratio remains the same. The original price of the second article is:
  • a)
    Rs.40
  • b)
    Rs.35
  • c)
    Rs.10
  • d)
    Rs.30
Correct answer is option 'A'. Can you explain this answer?

Tarun Chawla answered
Given:
The prices of two articles are in the ratio 3 : 4.

Let:
Let the original price of the first article be 3x and the original price of the second article be 4x.

According to the question:
If the price of the first article is increased by 10%, the new price becomes 3.3x.
If the price of the second article is increased by Rs. 4, the new price becomes 4x + 4.

Given:
The new ratio of the prices is still 3.3 : (4x + 4).

Equating the ratios:
3.3 / (4x + 4) = 3 / 4

Solving the equation:
12.4 = 3(4x + 4)
12.4 = 12x + 12
12.4 - 12 = 12x
0.4 = 12x
x = 0.4 / 12
x = 0.0333

Calculating the original price of the second article:
Original price of the second article = 4x
= 4 * 0.0333
= Rs. 0.1333
Therefore, the original price of the second article is Rs. 40.

Fresh fruits contain 75% while dry fruits contain 20% water. If the weight of dry fruits is 300 kg, what was its total weight when it was fresh?
  • a)
    900kg
  • b)
    850kg
  • c)
    920kg
  • d)
    960kg
Correct answer is option 'D'. Can you explain this answer?

Engineers Adda answered
Quantity of water in 300 kg dry fruits, = (20 /100) *300 = 60 kg
Quantity of fruit alone= 300-60 =240 kg
25 kg fruit piece in 100 kg fresh fruits
For 240 = (100 *240)/25 = 960 kg.

The tank-full petrol in Arun’s motor-cycle last for 10 days. If he starts using 25% more every day, how many days will the tank-full petrol last?
  • a)
    4
  • b)
    6
  • c)
    8
  • d)
    10
Correct answer is option 'C'. Can you explain this answer?

Engineers Adda answered
Assume – Arun’s motorcycle uses 1L per day and therefore tank’s Capacity = 10L.
25% increased per day= 1+(25/100) = 5/4 ie. 1.25L per day
Days = 10/1.25 = 8

Weights of two friends A and B are in the ratio of 1:2. A’s weight increases by 20% and the total weight of A and B together becomes 60 kg, with an increase of 30%. By what percent the weight of B increase?
  • a)
    30%
  • b)
    35%
  • c)
    40%
  • d)
    45%
Correct answer is option 'B'. Can you explain this answer?

Telecom Tuners answered
weight of A is x and weight of B is 2x
given that 60 kg weight is the 30% percent increase of the original weight, so
(130/100)*W = 60, W = 600/13 kg (W = original weight)
X + 2x = 600/13, x = 200/13
So weight of A = 200/13 and of B = 400/13
(120/100)*(200/13) + [(100 + a)/100]*(400/13) = 60
Solve for a. We will get a = 35%

A reduction of 20% in the price of rice enables a housewife to buy 5 kg more for rupees 1200. The reduced price per kg of rice
  • a)
    36
  • b)
    45
  • c)
    48
  • d)
    60
  • e)
    None of these
Correct answer is option 'C'. Can you explain this answer?

Iq Funda answered
Step-by-Step Solution
  1. Define Variables:
    • Let p = Original price per kg of rice (₹)
    • Reduced price = 20% less than original price = 0.8p
  2. Determine Quantity Purchased:
    • With original price:
      • Quantity bought = Total Money / Original Price = ₹1,200 / p = 1200/p kg
    • With reduced price:
      • Quantity bought = Total Money / Reduced Price = ₹1,200 / (0.8p) = 1500/p kg
  3. Set Up the Equation Based on the Increase in Quantity:
    • Difference in quantity = 5 kg
    • Therefore, 1500/p - 1200/p = 5
    • Simplify the equation:
      • 300/p = 5
    • Solve for p:
      • p = 300 / 5 = ₹60
  4. Calculate the Reduced Price:
    • Reduced price = 0.8 x Original price = 0.8 x ₹60 = ₹48
Conclusion
The reduced price per kg of rice is ₹48, which corresponds to Option c).

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